Ntiv tes sib koom ua ke board yog ib hom txiv neej ua board ua los ntawm ntoo strips txog tsib centimeters dav. Qee tus neeg tsis paub ntau txog cov pob qij txha, yog li kuv yuav qhia koj paub yuav ua li cas txheeb xyuas cov ntiv tes yooj yim. Txheeb xyuas cov ntiv tes sib koom ua ke, feem ntau saib nws cov khoom tseem ceeb loj hlob rings, cov ntiv tes sib koom ua ke feem ntau yog ua los ntawm cov ntoo fir, cov nplhaib loj hlob zoo dua, qhov loj dua txhua xyoo rings, ntev tsob ntoo muaj hnub nyoog, cov khoom zoo dua qub. ntiv tes sib koom board.
Lwm txoj hauv kev ua qhov no yog saib cov cim ntawm cov hniav. Cov ntiv tes sib koom phaj feem ntau yog muab faib ua cov hniav qhib thiab cov hniav tsaus, cov ntiv tes sib koom phaj nrog cov hniav tsaus yog qhov zoo dua, vim tias cov ntiv tes sib koom ua ke ntawm cov hniav qhib yog feem ntau ua rau qee qhov tsis sib xws tom qab tha xim, thiab tau kawg, kev ua haujlwm cov hniav tsaus yog qhov nyuaj dua. Cov ntoo yog ib qho nyuaj, thiab cov ntiv tes sib koom ua ke yog qhov zoo, vim tias nws qhov deformation tsawg dua li ntawm cov laug cam, thiab cov qauv zoo nkauj dua.
